To correct the white balance of your image in raw you need to simply click into the White Balance Tool at the top of the left hand side of your pane. Your mouse will change to a small pipette. You simply choose an area of your image you think is the correct White Balance and click, this will have changed your White Balance, if your still not happy with the White Balance you can adjust the temperature slider on the right hand side panel.
Corrected White Balance.
You can also use the Tone Curve tool to correct different areas of the image White Balance if required.
You will find the Tone Curve on the right hand side panel.
Once you are happy with your White Balance you are ready to Import your image (open image)